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Waiting for the Higgs Particle

WHEN rumors started crisscrossing the Internet last week that the elusive Higgs particle had been detected by researchers at the Large Hadron Collider outside Geneva, I experienced my first physics-generated chill in a decade. It happened again Tuesday morning with the official announcement suggesting that the more than 40-year search for the Higgs may finally be nearing its end.

The researchers have cautioned that the data have not yet reached the threshold for claiming a definitive discovery. But the stakes are so high that even the tentative announcement has rightly fueled much excitement. Finding the Higgs particle would complete an essential chapter in our quest to understand the basic constituents of the universe.

The story began in the 1960s as physicists developed what would soon be called “the standard model of particle physics” — a mathematical framework that would prove capable of predicting the results of every experiment at every atom smasher around the world. The equations locked quarks and electrons, muons and neutrinos and a host of other fundamental particles into a mathematical matrix whose intrinsic patterns, like the form of a perfect snowflake, exhibited an exacting symmetry.

But even as the theory’s predictions were repeatedly borne out by nearly half a century of experimental data, one vital part remained beyond reach.

The theory incorporated a proposal, most closely associated with the English physicist Peter Higgs, for how fundamental particles acquire mass. Roughly speaking, the mass of a particle, much like the mass of a truck, is the resistance you’d feel were you to push on it. The question is, where does this resistance come from? The answer, according to Higgs’s idea, is that all of space is filled with an invisible substance — the Higgs field — which acts kind of like a pervasive molasses, exerting a drag force as particles try to accelerate through it. The “stickier” a particle is, the more the molasses-like Higgs field affects it, and the more massive the particle appears.

The emptiest of empty space, vacuumed clean of matter and radiation, would still be permeated by the Higgs field. Higgs thus suggested a rewriting of the very definition of nothingness, filling otherwise empty space with a substance capable of bestowing upon particles their mass.

It was a strange and exotic proposal; the first paper Higgs submitted on the subject was rejected. But as physicists continued to study the idea, they found its mathematical simplicity and physical insights remarkable. Other approaches to providing particles’ mass fell afoul of one or another mathematical inconsistency, whereas Higgs’s proposal endured. By the time I entered graduate school in the 1980s, the Higgs field was routinely spoken of with such nonchalance that for a while I didn’t realize the idea had yet to be experimentally confirmed.

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But however mathematically enticing a theory may be, experimental confirmation is essential. And that was one of the main reasons for building the Large Hadron Collider, a 17-mile-long tubular track buried a few hundred meters under Geneva that winds its way across the Swiss-French border and back again. The collider accelerates protons along the track in opposite directions to nearly the speed of light, and each second slams millions of them together in head-on collisions. Calculations show that these collisions may be sufficiently violent to “chip off” a minuscule chunk of the Higgs field, which would appear as a tiny particle: the Higgs. (More precisely: the energy of the colliding protons may transmute into a Higgs particle.)

But the calculations also made clear that finding this particle would be no easy task. The Higgs particle would be short-lived, quickly decaying into other, more familiar particles (like photons, particles of light), and only by examining the decay products could the researchers accumulate evidence for the Higgs. What’s more, the powerful proton collisions produce a maelstrom of other particulate debris, and so the challenge of pinpointing the Higgs is enormous.

Thousands of scientists have dedicated decades of their lives to doing just that. This week’s announcement does not yet rise to a definitive discovery because a statistical fluke could be masquerading as a Higgs particle. But interest in the findings has been high, in part because not one but two independent and competitive groups, each analyzing collider data obtained from separate detectors, seem to be homing in on the same result. While the official line is, rightly, one of cautious optimism, the excitement, especially behind closed doors, is palpable.

Within a year, additional data should settle the question. Perhaps the finding will be disproved. That’s the nature of cutting-edge research. But if confirmed, wow. The legions of physicists, engineers and computer scientists, whose collective efforts created the Large Hadron Collider, will have revealed the deepest layer of reality our species has ever probed.

For me, as a theorist standing outside the experimental effort, the result is no less exciting. Years ago, when I was in high school, my physics teacher gave the class a homework problem: calculating the trajectory of a ball swinging from the ceiling by a piece of chewing gum. That night, when I finished the calculation, I ran down the hallway to show my father — I was utterly and profoundly amazed that mathematical symbols scratched in pencil on a piece of paper could describe things that actually happened in the real world. That’s when I became hooked on physics. With Tuesday’s announcement, tentative though it may be, I’m awed yet again.

Brian Greene, a professor of physics and mathematics at Columbia, is the author of “The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos.”

A version of this op-ed appears in print on December 15, 2011, on Page A39 of the New York edition with the headline: Waiting for the Higgs Particle. Today's Paper|Subscribe